Vinyl chloride resins have good physical properties and generally have satisfactory molding characteristics, although the use of a plasticizer and/or a high processing temperature is frequently required (U.S. Pat. No. 3,925,510). However, they have a relatively low softening temperature, e.g. 65.degree.-75.degree. C., and when a large amount, up to about 30 percent, of a relatively low molecular weight plasticizer is added to improve processability and flexibility, the softening temperature may be significantly reduced, e.g. to 60.degree. C. or lower. In the past, various copolymers or terpolymers with higher softening temperatures than a vinyl chloride resin have been blended into the vinyl chloride resin in order to provide good dimensional stability at a higher temperature.
It is well-known that a polyblend of a vinyl chloride resin with an ABS resin (a graft copolymer of styrene, acrylonitrile, and rubber, usually butadiene-based) has a higher softening temperature than that of the vinyl chloride resin. For example, U.S. Pat. No. 3,626,033 shows that a blend of a vinyl chloride resin and an ABS resin in a 75:25 ratio exhibits a softening temperature of 77.5.degree. C., compared with 71.5.degree. C. for the vinyl chloride resin alone. The addition of 20 percent of a copolymer of styrene and maleic anhydride as a third component further increased the softening temperature to 91.degree. C. My U.S. Pat. Nos. 4,469,844 and 4,469,845 summarize prior art on blends containing vinyl chloride resins and various rubber-modified and unmodified copolymers of styrene, maleic anhydride, and optionally up to 25 weight percent of acrylonitrile or methyl methacrylate. The blends could optionally contain an ABS resin or an MBS resin ( a graft copolymer of styrene, methyl methacrylate and a rubber).
U.S. Pat. Nos. 4,469,844 and 4,469,845 also describe improved polyblends of rubber-modified vinyl chloride resins (graft copolymers of vinyl chloride and a rubber) with rubber-modified or unmodified copolymers of a vinyl aromatic monomer, maleic anhydride, and optionally up to 25 weight percent of acrylonitrile or methyl methacrylate, the polyblends optionally containing ABS, MBS, or an ungrafted rubber. Such polyblends exhibited higher softening temperatures than that of the vinyl chloride resin. U.S. Pat. No. 4,454,300 describes polyblends of graft copolymers of vinyl chloride and polyolefin rubbers.
Various copolymers of styrene and imide derivatives of maleic anhydride have been blended with unmodified vinyl chloride resins in order to obtain increased softening temperatures. U.S. Pat. No. 4,339,554 describes polyblends containing copolymers of styrene and maleimide. U.S. Pat. No. 4,458,046 describes polyblends of vinyl chloride resins with copolymers of styrene and imide derivatives, optionally containing impact modifiers. U.S. Pat. No. 3,652,726 describes a polyblend of a rubber-modified terpolymer of styrene, N-2-chlorophenyl maleimide, and acrylonitrile (weight ratio of 62:9:29) with a vinyl chloride resin in an 80:20 weight ratio. The blend exhibited a Vicat softening temperature of 88.degree. C. and had high impact strength. Bourland and Wambach (Journal of Vinyl Technology, Vol. 5, No. 3, p. 121, September, 1983) disclosed the preparation of blends of unmodified vinyl chloride resins and copolymers of styrene and maleic anhydride. Softening temperatures were intermediate between those of the two components.
U.S. Pat. No. 4,255,322 describes the peparation of polyblends of vinyl chloride resins with polyglutarimides which exhibited softening temperatures higher than that of the vinyl chloride resin. The blends were transparent because of the compatibility of the polyglutarimides and vinyl chloride resins. Impact-resistant blends could be prepared by the addition of impact modifiers such as MBS, ABS, coplymers of ethylene and vinyl acetate (EVA), and a graft copolymer of methyl methacrylate and a butyl acrylate-based rubber. Transparent impact--resistant blends could be prepared by the use of MBS with a refractive index which matched that of the blend. Preferred glutarimides used in the blends of U.S. Pat. No. 4,255,322 were those prepared from acrylic polymers such as methyl methacrylate and copolymers thereof by reaction in an extruder reactor with ammonia or methyl amine, according to the method described in Belgian Pat. No. 848,486. Preferred polymers had degrees of imidization of 20 to 60 percent.
Polyglutarimides prepared from polymethyl methacrylate and ammonia have also been blended with other polymers to provide increased softening temperatures. A 60:40 blend of a polyglutarimide with MABS (graft polymer of styrene, acrylonitrile, methyl methacrylate, and rubber) exhibited a heat distortion temperature of 134.degree. C. and had good transparency (Chem. Abst. 99:196,046f, 99, p. 45, 1983). A 50:30:20 blend of a polyglutarimide, ABS, and an ungrafted terpolymer of styrene, alpha-methylstryene, and acrylonitirile exhibited a heat distortion temperature of 123.degree. C. (Chem. Abst. 99:196,047g; 99, p. 45, 1983), A 50:30:20 blend of polyglutarimide, ABS, and an ungrafted terpolymer of styrene, maleic anhydride, and acrylonitrile exhibited a heat distortion temperature of 129.degree. C. (Chem. Abst. 99:196,048h; 99, p. 45, 1983).